1. Field of the Invention
The invention relates to alignment devices and in particular to alignment devices for aligning apertures in different plates.
2. Description of the Related Art
FIG. 1 is a cross-section of an ion generator. The ion generator comprises an arc chamber (ion generation chamber) 10 for the formation of ions 12. The ions extracted from the arc chamber 10 through an aperture 22 of a plate 20 and an aperture 32 of a plate 30 become ion beams (not shown). In the ion generator, the plates 20 and 30 provide electrical potential to the ion beam to focus or scatter the ion beam, and thus, act as a G1 electrode and a G2 electrode respectively.
The plate 20 is typically combined with the arc chamber 10 and acts as a front face thereof, while the plate 30 is movable and typically fastened on a supporter 50 during operation of the ion generator. It is thus important to align the plate 30 with the plate 20, specifically to align the aperture 32 with the aperture 22. The resulting ion beam deviates as the aperture 32 deviates. The deviated ion beam cannot be introduced to a predetermined position of a target (not shown) such as a semiconductor substrate, negatively affecting the process yield.
FIG. 2 shows a conventional alignment device for aligning the aperture 32 with the aperture 22. The alignment device comprises a body 40, one alignment pin 41, and two alignment pins 42. Pins 41 and 42, extending from the body 40, respectively comprise arrow-like heads 41a and 42a fitting the widths of the apertures 22 and 33 respectively. The pin 41 is between the pins 42.
FIG. 3 is a top view showing alignment of the plate 30 with the plate 20 utilizing the alignment device shown in FIG. 2, wherein the body 40 is ignored. The central pin 41 extends through the aperture 32 to the aperture 22, while the pins 42 extend to the aperture 32. When the arrow-like heads 42a both completely fit the width of the aperture 32, the operator detects position of the arrow-like head 41a. This design asserts that the arrow-like head 41a completely fits the width of the aperture 22 when it extends to a predetermined position, and the apertures 22 and 32 are successfully aligned when the detection results show the arrow-like head 41a completely fitting the width of the aperture 22 under the condition that the arrow-like heads 42a both completely fit the width of the aperture 32.
As shown in FIG. 3, the plate 30 further comprises a root portion 35 fastened to the supporter 50 with a screw 52. When the plate 30 laterally rotates utilizing the screw 50 as a pivot as shown in FIG. 3, the arrow-like heads 42a may both completely fit the width of the aperture 32, and the arrow-like head 41a may simultaneously completely fit the width of the aperture 22. In this case, the apertures 32 and 22 are not aligned, but the conventional alignment device may misdirect the operator to mistakenly determine the apertures 32 and 22 are optimally aligned, resulting in deviation of the ion beam during operation of the ion generator.
Further, the arrow-like heads of the pins 41 and 42 can potentially cause other problems. For example, the central tip 41b of the arrow-like head 41a is designed to be disposed at the center line of the aperture 22 during alignment. As shown in FIG. 4, however, the central tip 41b potentially deviates from the center line of the aperture 22 during alignment, but it is difficult to detect this deviation because the plate 20 is at a deeper position than the operator's point of view. In some cases, the detection of the central tip 41b is manually performed by the operator's naked eye, and the light illumination and the operator's viewpoint potentially misdirect the operator's determination to the position of the central tip 41b, leading to failure of alignment.
The alignment procedures utilizing the device shown in FIG. 2 are complicated and time-consuming due to the described inconvenience introduced thereby. The alignment of the plates 30 and 20 utilizing the conventional alignment device typically requires between 1 and 2 minutes, negatively affecting product throughput and man hours.
In some cases, the abnormal utilization and handling of the conventional alignment device shown in FIG. 1 can potentially cause damage thereto. For example, accidental impact to the pins 41 and 42 incurred in a drop can potentially bend or deform the pins 41 and/or 42 with damage often not visible to the naked eye. Thus, the operator may utilize the deviated device to perform the alignment, and the alignment steps lead to misalignment of the plates 20 and 30. Further, the bent or deformed pins 41 and/or 42 cannot be repaired, and thus, it is necessary to scrap the deviated device and purchase a new one costing approximately 150 US dollars or more, negatively affecting the product cost.
As described, the alignment failure modes of utilization of the conventional alignment device are various and complicated. When ion beam deviation occurs, the repair is time-consuming, negatively affecting product throughput.